What finally caused Germany defeat during world war 1?

Germany lost the war because it was overwhelmed by surmounting enemy forces; it was out of soldiers and ideas, and was losing ground every day by October 1918. Nevertheless, it was still in France when the war ended on Nov. They were outnumbered, and their opponents had access to much greater resources. Therefore, Germany's best hope of winning was a rapid knock-out blow, destroying their enemies' armies quickly and then forcing a peace. If the war bogged down in stalemate, then the Allies' greater depth of resources would allow them to grind Germany down through attrition and defeat them. The French army was able to escape the trap set for them by the Schlieffen Plan, redeploy their forces to the Marne, and halt the German advance in September 1914.

Germany lost the war because it was overwhelmed by surmounting enemy forces; it was out of soldiers and ideas, and was losing ground every day by October 1918.